1. Field of the Invention
The present invention relates to an optical waveguide preferably used for a touch panel and an optical touch panel.
2. Description of the Related Art
Conventionally, an optical waveguide which comprises: cores including a light incident core having an end and a light emitting core having an end; an under-cladding layer for supporting the cores; and an over-cladding layer with a convex lens portion having a side cross-sectional shape of substantially a quarter of a circle is known (For example, JP 2008-203431 A). In such an optical waveguide, diverging light emitted from the ends of the cores can be converted into parallel light in the convex lens portion. Further, parallel light having a great width incident upon the surface of the convex lens portion can focus light on the ends of the cores in the convex lens portion. As a result, a high optical transmission efficiency can be obtained.
Generally, in optical touch panels, infrared rays are used for a touch detection, so that touch detection may be not possible when strong outside light, such as sun light is incident on a detection part. Optical touch panels with conventional optical waveguides have not sufficiently resolved a problem of a reduction in touch detection accuracy.